1. Technical Field
The present invention relates to a liquid crystal display device for forming an image and a projector having the liquid crystal display device.
2. Related Art
In the past, liquid crystal projectors using a twisted-nematic liquid crystal panel were known in which two sheets of optical compensating elements formed of a sapphire plate having an optical axis parallel to a rubbing direction and tilted by a predetermined angle about an incidence surface are disposed between a liquid crystal panel and an incidence polarizing plate or an emission polarizing plate (see JP-A-2004-198650).
However, in order to determine the thickness of the optical compensating elements in the above-mentioned liquid crystal panel, it is necessary to know information such as how the liquid crystal molecules rise upright in an actual black display, what alignment distribution the light has, and what the polar angle of the optical axis of the optical compensating element is. Particularly, it can be obtained by simulation how the liquid crystal molecules rise upright, but it requires many parameters of the liquid crystal panel, such as a liquid crystal refractive index, a difference in refractive index, a pretilt angle, a twist angle, a cell gap, a dielectric constant, and a helical pitch. As a result, it is necessary to consider many parameters to determine the thickness of the optical compensating element and it is also necessary to repeat complex calculations even with a slight change in design.
When a sapphire plate is sued as the optical compensating element, the difference in refractive index from the quartz glass constituting the liquid crystal panel is greater than that of a quartz plate, thereby making it difficult to optically compensate for an obliquely incident light beam. Sapphire is more expensive than materials such as quartz, thereby increasing the cost for the optical compensating element. In addition, sapphire has hardness higher than the material such as quartz and it is difficult to process sapphire.